It is well known that when water freezes to solid ice it undergoes an expansion in volume of about 9% and this physical change has been the cause of many instances of bursting of water pipes. There have been many solutions to this problem. In residential homes where freezing temperatures occur at some time during the year it has been normal to make sure that all water piping is insulated or otherwise kept from being subjected to freezing temperatures by putting such pipes under ground or inside houses which are heated to prevent freezing temperatures from occurring. In instances where insulation is not practical the freezing temperature of the water could be changed by introducing the antifreeze solution into the water, the pipes could be jacketed with heating coils or other means to keep the temperature of the water above freezing.
Still other means have been attempted in the past to prevent freeze damage to pipes containing water or other liquids which will freeze. In U.S. Pat. No. 2,409,304 to Morrison there is a disclosed central compressible core which is placed inside a pipe containing water and which provides an internal expansion volume to accomodate the volume needed when the water freezes.
This means is satisfactory in a general sense, but in order to accomodate water piping in a practical way it leaves much to be desired. The turns, couplings and other fittings in modern piping do not lend themselves to having a continuous length of compressible core as shown in this prior art. Furthermore the liquid pressure is such that compressible cores might be so compressed that little safety volume would remain for that needed when the water freezes. Still further, the compressible core may tend to move away from its required position due to the velocity changes of the flowing water in the pipe.
It is an object of this invention to provide an improved means for preventing freeze damage to liquid conduits by employing the concept of a central compressible core in a new way.